1. Field of the Invention
The present invention relates to apparatus for scanning a multicolor original and producing electrical signals indicative of the color image information of the original. More particularly the present invention relates to such scanning apparatus, and scanning/printing apparatus, using light valve arrays.
2. Description of the Prior Art
Recently, it has been found that light valve array devices provide a highly useful vehicle in electronic imaging. One preferred light valve configuration comprises a piece of ferro-electric ceramic material, such as lanthanum-doped lead zirconate titanate (PLZT), which is sandwiched between crossed polarizers and electrically activatible to operate in a Kerr cell mode. An array of such light valves comprises such crossed polarizers and a panel of PLZT material that has a plurality of electrodes formed on one of its major surfaces. The electrodes are arranged in a manner facilitating the selective application of discrete electrical fields across (in a direction perpendicular to the direction of viewing) discrete surface areas which constitute pixel portions of the panel. Upon application of such fields, the PLZT material becomes birefringent and rotates the direction of polarization of incident light by an extent dependent on the field magnitude. This results in transmission of light through the PLZT pixels and cooperating polarizers varying as a function of the respective addressing fields.
U.S. Pat. No. 4,229,095 discloses various embodiments of electronic color-imaging apparatus that utilize such light valve arrays to effect multicolor exposure of panchromatic recording media. For example, a color image is formed electronically by selectively opening and closing individual light valves of such arrays in synchronization with the energization of red, green and blue exposing sources and according to the red, green and blue color information for the pixels of that image. One preferred embodiment disclosed in that patent comprises a linear light valve array disposed in spaced transverse relation to the recording media feed path. The pixels of the array are addressed concurrently with image information, a line at a time, and the movement of the recording medium, and the red, green and blue color exposures are synchronized with successive actuations of the linear array.
In electronic color imaging devices of the kind described in U.S. Pat. No. 4,229,095 and in other kinds of electronic imaging apparatus (see e.g. U.S. Pat. Nos. 4,125,322 and 4,168,118), it is necessary to provide an information signal(s) containing color image information representative of the image to be reproduced. Usually, such information signal(s) are produced by scanning an original image.
One common mode for effecting such scanning is with a scanning light beam (e.g. a laser beam) sequentially deflected (e.g. with a polygon mirror or an acoustooptic cell) across successive lines of the original. An optical system is adapted to direct scan beam light (reflected from or transmitted by the original) to a photodetector which produces an electrical signal representative of the scanned original. In multicolor imaging, separate scans are effected (e.g., with red, green and blue light beams) to provide separate color signals.
Another common technique to effect such optoelectric scanning of an original is with a solid state light sensor array, e.g. a charge coupled device (CCD). Such solid state devices can sense in parallel, and store, the light-dark condition of all picture elements (pixels) of a line of the original. The pixel information is then clocked out serially to provide an electrical signal representative of that image line. Different color filters can be used in cooperation with such solid state sensor arrays to generate separate electrical signals for the different individual colors necessary to form a multicolor image.